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ERR(3) FreeBSD Library Functions Manual ERR(3)
NAMEerr, verr, errc, verrc, errx, verrx, warn, vwarn, warnc, vwarnc, warnx,
vwarnx, err_set_exit, err_set_file -- formatted error messages
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS#include <err.h>
voiderr(inteval, constchar*fmt, ...);
voiderr_set_exit(void(*exitf)(int));
voiderr_set_file(void*vfp);
voiderrc(inteval, intcode, constchar*fmt, ...);
voiderrx(inteval, constchar*fmt, ...);
voidwarn(constchar*fmt, ...);
voidwarnc(intcode, constchar*fmt, ...);
voidwarnx(constchar*fmt, ...);
#include <stdarg.h>
voidverr(inteval, constchar*fmt, va_listargs);
voidverrc(inteval, intcode, constchar*fmt, va_listargs);
voidverrx(inteval, constchar*fmt, va_listargs);
voidvwarn(constchar*fmt, va_listargs);
voidvwarnc(intcode, constchar*fmt, va_listargs);
voidvwarnx(constchar*fmt, va_listargs);
DESCRIPTION
The err() and warn() family of functions display a formatted error mes-
sage on the standard error output, or on another file specified using the
err_set_file() function. In all cases, the last component of the program
name, a colon character, and a space are output. If the fmt argument is
not NULL, the printf(3) -like formatted error message is output. The
output is terminated by a newline character.
The err(), errc(), verr(), verrc(), warn(), warnc(), vwarn(), and
vwarnc() functions append an error message obtained from strerror(3)
based on a code or the global variable errno, preceded by another colon
and space unless the fmt argument is NULL.
In the case of the errc(), verrc(), warnc(), and vwarnc() functions, the
code argument is used to look up the error message.
The err(), verr(), warn(), and vwarn() functions use the global variable
errno to look up the error message.
The errx() and warnx() functions do not append an error message.
The err(), verr(), errc(), verrc(), errx(), and verrx() functions do not
return, but exit with the value of the argument eval. The err_set_exit()
function can be used to specify a function which is called before exit(3)
to perform any necessary cleanup; passing a null function pointer for
exitf resets the hook to do nothing. The err_set_file() function sets
the output stream used by the other functions. Its vfp argument must be
either a pointer to an open stream (possibly already converted to void *)
or a null pointer (in which case the output stream is set to standard
error).
EXAMPLES
Display the current errno information string and exit:
if ((p = malloc(size)) == NULL)
err(1, NULL);
if ((fd = open(file_name, O_RDONLY, 0)) == -1)
err(1, "%s", file_name);
Display an error message and exit:
if (tm.tm_hour < START_TIME)
errx(1, "too early, wait until %s", start_time_string);
Warn of an error:
if ((fd = open(raw_device, O_RDONLY, 0)) == -1)
warnx("%s: %s: trying the block device",
raw_device, strerror(errno));
if ((fd = open(block_device, O_RDONLY, 0)) == -1)
err(1, "%s", block_device);
Warn of an error without using the global variable errno:
error = my_function(); /* returns a value from <errno.h> */
if (error != 0)
warnc(error, "my_function");
SEE ALSOexit(3), fmtmsg(3), printf(3), strerror(3)HISTORY
The err() and warn() functions first appeared in 4.4BSD. The
err_set_exit() and err_set_file() functions first appeared in
FreeBSD 2.1. The errc() and warnc() functions first appeared in
FreeBSD 3.0.
FreeBSD 10.1 March 6, 1999 FreeBSD 10.1